Team reserve driver Nick Heidfeld said a decision has not been taken about whether the device, activated in the cockpit by the driver and designed to spoil the downforce to the rear wing on straights, will stay on the W01 for qualifying and the race.

"It is now being analysed to see whether we use it on both cars for the rest of the weekend," Heidfeld told the German broadcaster Sky.

The 32-year-old said he thinks the system works well, after the wind tunnel data looked "promising".

Meanwhile, unlike the sidepod-mounted inlet on the Sauber, and McLaren's on the upper monocoque, Ferrari's new F-duct system lets air in via the actual engine cover itself.

Following his engine failure on Friday morning, Spaniard Fernando Alonso returned to the Shanghai track for the afternoon session with the V8 he used to win in Bahrain last month.